None of the nine gecko species found in the Hawaiian Islands evolved there. Some, such as the stump-toed gecko and the Indo-Pacific tree gecko, came over with the first settlers; others, including the orange-spotted day gecko and the tokay gecko, appeared more recently, most likely a result of illegal pet trafficking. But the state's tropical climate, lush habitats and abundant insect life proved hospitable for these lizards, as most of these species are now established on one or more of the islands.
TL;DR (Too Long; Didn't Read)
To protect Hawaii's diverse native wildlife, all gecko species are prohibited from entry to the state or possession by individuals. The state operates an Amnesty Program, whereby individuals can drop off illegal animals without threat of fine or prosecution. Animals surrendered through this program will not be euthanized. To date, the Department of Agriculture has seized or been given many reptiles, including many leopard geckos, an aggressive feeder that is native to Iran, India, Afghanistan and Pakistan. No wild populations of leopard gecko have been found in Hawaii.
Gehyra mutilata, commonly known as the stump-toed or four-clawed gecko, probably stowed away with early Polynesian settlers of the Hawaiian Islands. Endemic to tropical Asia, the tiny gray to grayish-brown nocturnal gecko is now established on the main Hawaiian Islands, as well as Lanai and Kahoolawe. This gecko is equally at home in both natural and urban habitats, often spotted on lumber piles, under rocks, beneath tree bark and on buildings close to light. Like other lizards, the stump-toed gecko can regrow a lost tail. But far more unusual is their practice of twisting free from predators by tearing off patches of skin. Once relatively common, the species has been displaced by the common house gecko.
The Indo-Pacific gecko, Hemidactylus garnotii, and its cousin the common house gecko, Hemidactylus frenatus, are small, nocturnal geckos. Both share the same diet of insects and are similar in size with gray coloring, though the Indo-Pacific gecko belly runs yellowish-orange. Like the stump-toed gecko, the Indo-Pacific gecko is thought to have come to the islands with early settlers. Today, it's found on all Hawaiian islands both large and small. The entire population is female, reproducing through a process known as parthenogenesis, whereby young develop from unfertilized eggs.
True to its name, the common house gecko is Hawaii’s most common gecko, inhabiting both urban and forested habitats on all the larger islands as well as Lanai and Kahoolawe. It was first recorded in Hawaii in 1951 and since then has rapidly displaced the stump-toed and Indo-Pacific geckos.
Indo-Pacific Tree Gecko
Native to tropical Asia, the Indo-Pacific tree gecko, Hemiphyllodactylus typus, is established on all the larger Hawaiian islands as well as the island of Lanai. The smallest of the state's geckos, the 2- to 3-inch-long, gray-brown lizard feeds on tiny insects at night, often on the trunks of trees in forested areas and valleys. Like the Indo-Pacific gecko, the population is entirely female. Already rare, the tree gecko's numbers seem to be decreasing due to loss of habitat, competition and predation by larger geckos.
Lepidodactylus lugubris complex, commonly known as the mourning gecko, is another one of the island's early settlers. And as with the Indo-Pacific gecko and the tree gecko, the Hawaiian population is all female. Unique to this species, females have been observed copulating with each other, hypothesized to be a demonstration of social rank or territorial superiority. The small, stout mourning gecko is gray-brown with darker chevron wave markings and a characteristic dark line connecting the eyes. Once common on all the large Hawaiian Islands as well as Niihau, Lanai and Kahoolawe, the species has been reduced in number by the more aggressive, and in many cases predatory, common house gecko.
Three species of the brightly-colored day geckos have found their way to the Hawaiian Islands. As of 2014, the state classifies all three Phelsuma species as injurious wildlife for fear they will compete with native birds for the same food source, namely insects and invertebrates.
In 1974, a student at the University of Hawaii released eight gold dust day geckos, Phelsuma laticauda laticauda, a native of Madagascar, into the Upper Mano Valley. Populations are now well-established in Oahu, Maui and Hawaii. The bright green lizard has beautiful blue-rimmed eyes, two or three red lines across its snout and, as the name implies, orange-gold spots across its neck and shoulders.
Similar in size and color, the orange-spotted day gecko, Phelsuma guimbeaui, a native of Mauritius, is well-established in Oahu, a result of deliberate or accidental release by pet owners or importers. Unlike its cousins, the orange-spotted day gecko has a blue patch on its shoulders and neck.
A native of Madagascar, the giant day gecko, Phelsuma madagascariensis grandis, was first found in Oahu in 1996. Bright green with splashes of orange on the head, neck and body, the day gecko is much larger than its cousins; adults can be 8 to 9 inches long and deliver a crushing bite.
Tokay Gecko and More
Growing up to 12 inches in length, the gray-blue and orange-spotted tokay gecko is one of the largest gecko species in the world. Because of the irresponsibility of pet owners, the Southeast Asian native is now firmly established in Oahu. Named for the distinct call of males of the species -- To-kay, To-kay -- the nocturnal gecko is aggressive and highly predatory. While they primarily feed on insects, they also consume bird eggs, putting native bird species at risk. Like the day geckos, the tokay is classified as injurious wildlife. Furthermore, the Oahu Invasive Species Council routinely surveys for the species and has established a hotline for reporting sightings.